Predicting Change

Site: 
Shrubs (Morella cerifera) growing behind a grassy dune on a barrier island in the VCR LTER site.
S. T. Brantley

VCR scientists are using this knowledge to forecast climate change effects on these fragile coastal landscapes. Plant ecological dynamics on barrier islands are a function of complex interactions and feedbacks between individual species, environmental factors, and geological processes. However, long-term studies of barrier island ecology in the VCR LTER site has revealed that the controls on plant community distribution can be simplified to two key environmental parameters: distance from the shoreline and elevation above sea level.

These two parameters integrate a number of important physical variables. For example, distance from the shoreline affects exposure to sea spray and burial by windblown sand, as well as vulnerability to storm-related disturbance (i.e., overwash) and, as a result, the extent to which ecological succession can take place. Elevation above sea level also determines disturbance vulnerability, and influences groundwater and nutrient availability; at the same time, plants (particularly dune-building grasses) can significantly affect elevation by trapping and accumulating sand.

Shoreline position and island topography are highly variable in both time and space among the VCR LTER barrier islands, resulting in similarly variable plant communities. Shrub thickets, the most stable barrier island plant communities, are intolerant of flooding and increases in groundwater salinity, both of which are caused by storm events and sea-level rise. Shrub thickets therefore serve as excellent sentinels for short-term barrier island change driven by storms and long-term change driven by rising sea level. Researchers in the VCR are using remote sensing (e.g., hyperspectral satellite imagery) and field studies of shrub thickets to assess and predict spatial patterns in the response of these systems to changing climate conditions.

Elevation and distance from the shoreline are key factors in determining vegetation dynamics on barrier islands in the VCR LTER site. Elevation determines the availability of groundwater for plants, with lower elevations more susceptible to flooding and higher elevations more vulnerable to stress from water scarcity. Distance from the shoreline modulates the extent to which salt spray, disturbance, and abrasion by windblown sand impact vegetation.
D. Young, 2011.
For further reading: 
Shao, G., D. R. Young and J. H. Porter. 1998. An integration of remotes sensing and GIS to examine the responses of shrub thicket distributions to shoreline changes on Virginia barrier islands. Journal of Coastal Research 14: 299-307.
Young, D. R., J. H. Porter, C. M. Bachmann, G. Shao, R. A. Fusina, J. H. Bowles, D. Korwan, and T. F. Donato. 2007. Cross-scale patterns in shrub thicket dynamics in the Virginia barrier complex. Ecosystems 10: 854-863.
Naumann, J. D., J. E. Anderson, and D. R. Young. 2008. Linking physiological responses, chlorophyll fluorescence and hyperspectral imagery to detect salinity stress using the physiological reflectance index in the coastal shrub, Myrica cerifera. Remote Sensing of Environments 112: 3865-3875.
For further information: 
Dr. Don Young
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